The present invention relates to an inflatable seatbelt system having a webbing at least a part of which is formed in the shape of a bag and which is maintained in a strap-like configuration under normal circumstances but, when an emergency situation occurs, inflates by the action of a gas supplied from a gas generating device.
Hitherto, seatbelt systems have been attached to the seats of many vehicles, for example, automobiles. A typical seatbelt system is arranged to restrain the occupant's body by a webbing upon the occurrence off, an emergency situation, e.g., a collision of the vehicle, thereby protecting the occupant from injury which would otherwise be done to him or her by collision with a part of the vehicle body. In such a seatbelt system, however, the width of the webbing, which constitutes a belt for restraining the occupant's body, is not so large. Therefore, the occupant's body locally receives a relatively heavy load when restrained by the webbing.
Under these circumstances, a variety of inflatable seatbelt systems have been proposed in which the webbing is formed in the shape of a bag, and under normal circumstances, the bag-shaped webbing is maintained in a strap-like configuration so as to function as an ordinary seatbelt, whereas, when an emergency occurs, the bag-shaped webbing is inflated by a gas introduced thereinto from a gas generating device so as to function as an air belt whereby the occupant's body is received by the inflated webbing. For example, see Japanese Patent Application Laid-Open (KOKAI) Nos. 47-26830 and 49-88220. Such an inflatable seatbelt system allows the kinetic energy of the occupant's body to be received by the webbing having a wider area. Thus, the load is dispersed, and hence the occupant's body receives a relatively light load. Accordingly, the occupant is protected even more effectively.
If it is intended to provide a rear seat with an air bag system as is provided for the occupant seated in the front seat, the air bag system must inevitably be provided on the front seat, which lies forwardly of the rear seat. However, if the air bag system is provided on the front seat, it is difficult for the air bag system to protect the rear seat occupant properly and effectively because the position in the longitudinal direction of the front seat depends on the occupant seated therein and the reclining position also differs according to circumstances. Accordingly, the above-described inflatable seatbelt system is particularly effective as a safety device for the rear seat.
Incidentally, various methods have heretofore been employed to maintain the bag-shaped webbing in a strap-like configuration under normal circumstances. For example, a method of maintaining a strap-like configuration is disclosed in the specification and drawings of U.S. Pat. No. 3,865,398. According to this method, both lateral margins W.sub.1 and W.sub.2 of a webbing W are folded, as shown in FIG. 11, and retained in their folded condition by a fastener or other appropriate engaging device F, thereby maintaining the webbing W in a strap-like configuration having a predetermined width. When the webbing W is to function as an air belt, a gas is supplied into the bag-shaped webbing W to inflate it. When the webbing W is inflated, the engagement made by the engaging device F is canceled by the expansion force. Consequently, the folded portions W.sub.1 and W.sub.2 are restored to their previous state, thereby allowing the webbing W to inflate to a large extent so as to provide an extremely larger width than the width of the webbing W when maintained in the strap-like configuration.
As another configuration maintaining method, for example, one such as that shown in FIG. 12 may be conceived. In this method, the bag-shaped webbing W is folded in the shape of a strap having a predetermined width in such a manner that the lateral margins W.sub.1 and W.sub.2 of the webbing W are reversed inward, and the webbing W is maintained in the strap-like folded condition by using a cover C. When the webbing W is inflated, the sewn part of the cover C is cut off by the expansion force, thereby allowing the webbing W to inflate to a large extent in the same way as the above-described configuration maintaining method.
These conventional configuration maintaining methods for the webbing W suffer, however, from some problems stated below. According to the conventional methods, the webbing W is first formed in a size which is the same as that of the webbing W when inflated, and the webbing W in this condition is folded and thereby maintained in the shape of a strap having a predetermined width so as to function as a seatbelt. Therefore, the webbing W in the folded state is unfavorably thick and bulky. For this reason, when the occupant fastens the seatbelt, the webbing W cannot snugly fit to the occupant's body, making the occupant feel uncomfortable. In addition, the seatbelt cannot smoothly be guided.
Further, since the webbing W is in a folded state, it cannot smoothly be inflated even when the gas is supplied into the bag-shaped webbing W.
In addition, the conventional methods need an operation of folding the webbing W and hence involve a large number of operating steps. Further, when produced, the webbing W needs to be cut into a width which is the same as the width thereof in the inflated condition. Therefore, a large amount of base fabric must be used.